The present invention is directed generally to pencils having an eraser tip, and more particularly to an improved pencil which provides an increased erasing capacity. The pencil has a threaded end which cooperates with a threaded ferrule which, as the eraser wears down, can periodically be screwed down to expose an unused portion of the eraser.
Pencils having various forms of eraser holders are well known in the art. For example, U.S. Pat. No. 174,466 shows a combined rubber eraser holder and point protector. A tube surrounds the eraser. A sleeve threadably cooperates with the tube and can be screwed up or down to uncover more or less of the rubber.
U.S. Pat. No. 737,070 illustrates an eraser tip for lead pencils. A cylinder may be screwed up or down on the sleeve to expose the desired amount of eraser. The sleeve slips over the end of the pencil.
U.S. Pat. No. 1,136,094 discloses an eraser holder for pencils. The holder is attached to the end of the pencil. Jaws are placed around the eraser, and the combination is screwed into the threaded holder. In another embodiment, a threaded tip is attached to the end of the pencil, and a threaded eraser is screwed into the tip.
U.S. Pat. No. 1,153,799 comprises an eraser tip for pencils. The device includes a cylindrical sheet metal tube or sheath, a cylindrical stick or erasive material which fits snugly inside the sheath, and a narrow sheet metal band or ferrule which encircles and tightly clasps the base of the eraser stick.
U.S. Pat. No. 1,237,013 consists of an eraser holder for pencils. As the eraser wears down, a frangible ferrule may be broken off to expose more of the eraser.
Conventional wooden pencils only have about {fraction (3/16)} of an inch of usable eraser. This means that most times the eraser is worn away while a large portion of the pencil remains. In these instances, a user is inclined to wastefully throw the pencil away. The present invention is directed to an improved pencil, which provides a user with more erasing capacity. In the present invention, the pencil and eraser tend to be worn equally, thereby dramatically extending the working life of the pencil. The extended eraser life of the present invention is effected by providing a threaded end on the pencil which cooperates with a threaded ferrule. The ferrule may be screwed progressively down on the threaded end as necessary to expose an unused portion of an elongated eraser.
In accordance with a preferred embodiment of the invention, the pencil includes an elongated body having an end which is sharpened, and an opposite end which is threaded. A threaded metal ferrule threadably engages the threaded end of pencil. An elongated rubber eraser is received by the ferrule and projects outward from the end of the pencil. When the eraser is worn down to near the end of the ferrule, the ferrule is screwed further onto the threaded end of the pencil thereby exposing an unused portion of the eraser. This process may be repeated numerous times during the working life of the pencil.
In accordance with an important aspect of the invention, the ferrule has at least one stop which engages the threaded end of the pencil. The stop permits the ferrule to be screwed down onto the threaded end for example in a clockwise direction, but prevents the ferrule from being unscrewed and removed from the pencil, for example in a counter clockwise direction.
In accordance with an important feature of the invention, the stop includes a pointed member or barb which digs into the threaded end when a user attempts to unscrew the ferrule.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.